Difference between scan_evt_handler and ble_evt_handler, impact of a Whitelist

RE: Difference between scan_evt_handler and ble_evt_handler, impact of a Whitelist

Edvin — Wed, 31 Mar 2021 09:33:45 GMT

It is correct that the whitelist is using hardware to filter the incoming advertisements/connection requests.

I don't remember whether or not the whitelist is the same for the advertising and the scanning. I guess you can experiment with that. Look at some examples that uses the whitelist.

peripheral/advertiser: ble_app_gls

central/scanner: ble_app_hrs_c

If you are scanning with a whitelist, then you will not get advertisement events from devices not in your whitelist. If you want that, you need to disable the whitelist.

If you think of it, if you want advertisements from all devices, is there really a point in using a whitelist?

In my opinion, the only real reason to use a whitelist is when you are advertising, and you know that you only want to connect to a known device, which is in your whitelist. It is always the central/scanner who initiates connections, so the only difference between scanning with and without a whitelist is that you will get more advertising report events when you don't use a whitelist.

Best regards,

Edvin

RE: Difference between scan_evt_handler and ble_evt_handler, impact of a Whitelist

pressure_sensor_nonconn_adv — Tue, 30 Mar 2021 11:30:18 GMT

Thank you for the explanations.

For the second question concerning the whitelist: From here I understood that when using a whitelist, the filtering is performed by hardware and nrf_ble_scan_on_ble_evt() is only called when the scanned packet is from a device on the whitelist.

-> But what about ble_evt_handler() does it still get called for packets that are NOT on the whitelist? In my application I am using a whitelist but would like to receive ADV_NONCONN_IND packets at the same time. Is this possible

RE: Difference between scan_evt_handler and ble_evt_handler, impact of a Whitelist

Edvin — Fri, 26 Mar 2021 14:10:08 GMT

Hello,

The ble_evt_handler() and scan_evt_handler() are a bit different, because the ble_evt_handler() receives events directly from the softdevice, while the scan_evt_handler()'s events are generated by the application (nrf_ble_scan.c).

Basically, the nrf_scan_handler is more related to some scan events, such as scan started, scan stopped, filter matched, and so on, while all the advertising packets generate events called BLE_GAP_EVT_ADV_REPORT which is usually handled in the nrf_ble_scan_on_ble_evt() in nrf_ble_scan.h. You could handle (or duplicate) these events in the ble_evt_handler as well, as these receive the same events. Look at how the nrf_ble_scan_on_ble_evt() in nrf_ble_scan.c is generating events for scan_evt_handler(), and how it handles the advertisement packets in the BLE_GAP_EVT_ADV_REPORT events.

Best regards,

Edvin